As noted above the invention relates to apparatus for protecting the environment from contamination. Although the preferred embodiment is directed to removal of oil from air exhausted from pneumatic devices it will be understood that the invention includes and has application to all forms of treatment processes directed to a fluid that is periodically or intermittently discharged, or is discharged at a varying rate. In each of these situations the system designer would traditionally design a system sized to treat continuously the maximum anticipated effluent flow rate. The present invention is capable of, in effect, storing the effluent and treating the effluent at a relatively low flow rate. Accordingly, the treating apparatus may be much smaller in capacity than apparatus that is sized to accommodate the maximum flow rate. The invention thus presents an opportunity to provide treatment apparatus that is much smaller than that apparatus that would be required in the case of apparatus designed for peak load conditions.
Although the invention has particular application to preventing industrial contamination of the atmosphere and particularly for protecting environment by (1) preventing the discharge of oil that would otherwise be present in the exhaust air discharged by industrial valves, cylinders and air motors and (2) limiting the noise pollution created by this same class of equipment incident to the noisy discharge of air those skilled in the art will recognize a wide variety of other applications. For example, the treatment of almost all fluids that are produced at a varying or cyclical rate may be facilitated by the apparatus of the present invention. This apparatus may be employed to temporarily store a fluid and then slowly discharge that fluid to a treating apparatus. Although the preferred embodiment of the invention includes a coalescing filter, it will be understood that some embodiments need not include a coalescing filter although most will include some filter or analogous structure.
Compressed air systems are used to provide compressed air to operate valves, cylinders, air motors and other devices. The compressed air may be supplied at 100 psi pressure and may be reduced to 20 psi or some other pressure. The compressed air is used as a controlled energy source and may enter a device and cause the device to do work such as open a valve, move a cylinder, close a damper, or cause other device operations. The compressed air stored in the operating portion of the device is expelled as it completes its expansion and work cycle. The air may be exhausted at some low pressure that may be 1 to 5 psi or some other pressure, The air quickly drops to ambient pressure as it enters the ambient air. This sudden drop in air pressure is accompanied by a very high level of noise generation. The frequency of this operation may occur several times a minute, several thousand times a day or any frequency required of the operation or device. The system may contain one or hundreds of these devices. The compressed air may fill the operator portion of the device in a small fraction of a second. The device may take 20 seconds between cycles. The end of the cycle results in the exhaust of this lower pressure compressed air that may for example be 1 psi. It may take, for example, 0.1 second for the exhaust to exit the exhaust port of the device.
The compressed air used to operate these devices picks up oil, used as a lubricant in the devices, and then exits the exhaust ports in the form of an oil laden aerosol mist. This invention addresses a practical means of removing the oil that otherwise would enter the local ambient environment of the plant where it could cause health and safety related problems.
The present invention is an offshoot of the apparatus described in several other patents having the same inventor as the inventor of the present invention. U.S. Pat. No. 4,827,719 deals with hydraulic oil systems is entitled "Closed Hydraulic System With Drying Means". U.S. Pat. No. 4,616,620 deals with engines and has been entitled "Contamination Control Apparatus". The third deals with the straining of sediment and the adsorption of oil out of waste water and is covered with U.S. Pat. No. 4,555,201 entitled "Sediment Dike" and a related patent pending. These prior inventions all include a bellows, bladder or flexible container and a desiccant dryer, absorber, filter or waste containment portion. The first two convert open systems to closed systems. The present invention relies on this background and the background described in the other patents having the same inventor as the present application.
Up until fairly recently the compressed air that operated pneumatic devices was simply exhausted to the ambient. In recent years concerns for personnel safety has prompted the use of coalescing type filters to remove the oil aerosols from the exhaust air. This exhaust air quickly reaches near ambient pressure and the filters may be exposed to a variable instantaneously pressure that increases then decreases to ambient pressure. Numerous types of filters can be used for this purpose. Almost any filter will help capture the oil. In some cases the oil is captured and retained in a sump. All prior art systems have a fixed system volume between the exhaust port of the device and the outlet of the filter. This causes the exhaust air to very quickly flow through the filter media at high velocity.
All known prior art methods route the exhaust directly to and through a filter media. Since the exhaust exits the devices at a very rapid rate the air pressure rapidly increases and then decreases until the air flows through the filter media. Therefore, the filtration takes place in a very short period of time. For example, 0.2 SCF may be exhausted in 0.1 seconds. This equates to a nominal flow rate of 2 SCFS or 120 SCFM. The filter media surface area and pressure drop capacity must be able to deal with the instant maximum pressure differential across the filter media thereby resulting in a greater filter surface area being required due to the very short duration of filtration time. The filtration efficiency at the higher pressures is less than at low pressures. These prior art systems are considered fixed volume open systems. High operating and maintenance costs are the result. Because of the high cost their use is limited.